The present invention relates to the synthesis of butane-1,4-diol and more particularly to its synthesis electrochemically from halohydrins.
A variety of chemical synthesis techniques are employed commercially to produce butane-1,4-diol; however, no successful electrochemical synthesis of butane-1,4-diol (herein often referred to as butanediol) has yet been developed. Cipris (Journal of Applied Electrochemistry, 8, 537-544 and 545-547, 1978) attempted the electrochemical reductive coupling of 2-chloroethanol and of 2-bromoethanol to form butanediol. No diol yield was realized by Cipris. Instead, ethylene, hydrogen gas, and ethers were the only products realized by the particular electrochemical reductive coupling method attempted. Cipris reports the use of predominantly anhydrous solvent systems containing at most up to about 5% water. Electrolytes used included tetraalkylammonium halides or para-toluenesulfonates, or lithium halides or para-toluenesulfonates. Sulfuric acid was the anolyte of choice.
Further study in electrochemical reductive couplings were conducted by Hall et al (J. Org. Chem., Vol. 41, No. 4, pp. 719-722, 1975; and Vol. 43, No. 22, pp. 4364-4366, 1978) on 1-bromooctane, 1-bromobutane, 2-bromobutane, and 2-bromo-2-methyl butane. Aluminum and nickel electrodes were studied with aluminum being the preferred cathode for use with a catholyte bath consisting of iron acetylacetonate, triphenyl phosphine, and tetrabutylammonium bromide. For an expanded discussion concerning reaction mechanisms for electrolytic reductions, reference is made to Hammett (J. Electrochem. Soc., 73, 523-538, 1938).
The present invention provides a method for electrochemically preparing butanediol which heretofore has eluded the art.